/Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/Operations/IntrinsicTriangulationMesh.h
Computes the angles based on the edge lengths, so must have valid EdgeLengths for this tri before calling. the order of the angles matches the order of the vertices that define the triangle, e.g. if (a, b, c) =GetTriangle()the (angle at a, angle at b, angle at c) = ComputeTriInternalAnglesR
FVector3d ComputeTriInternalAnglesR ( const int32 TID ) const